Plastic materials are predominantly used for interior package cushioning of shipped goods. Such plastic cushioning materials include a variety of polyethylene foams, moldable polyethylene copolymer foam, expanded polyethylene bead foam, styrene acrylonitrile copolymer foam, polystyrene foams, polyurethane foams, etc. Such plastic materials and plastic foams may be molded in place or molded to specific interior package cushioning structural shapes. The plastic may also be formed in pieces to provide loose fill, such as "styrofoam peanuts."
However, there are two major disadvantages associated with plastic cushioning materials and plastic interior package cushioning structures. First, disposable packaging is a major contributor to the nation's municipal solid waste. It is estimated that packaging constitutes approximately one third by volume of all municipal solid waste, and 8% of this amount is made up of cushioning materials. Second, plastic cushioning materials are generally neither biodegradable nor compostable and therefore remain a long-term component of the solid waste accumulation problem.
Furthermore, because of the nature of plastic molecules, plastic interior package cushioning structures have irreducible spring constant parameters that detract from product cushioning and protection from mechanical shock and vibration. Plastic foam materials may be inherently limited in the reduction that can be achieved for rebound, coefficient of restitution, and elasticity. As a result, the plastic cushioning materials may be implicated in resonance conditions which increase the shock amplification factor of the package system and link the shock acceleration, change of velocity, and displacement of the outer package with a product contained therein. Similarly, it has been found that these characteristics of plastic cushioning may contribute to vibration transmission and magnification under resonance conditions, and are an impediment to achieving critical structures for damping shocks and vibrations.
For these reasons, the inventor has determined that it would be desirable to provide novel and improved packaging structures, preferably constructed from molded paper fiber. These packaging structures are preferably constructed from recycled newsprint or other recycled paper products, and the structures are themselves recyclable. The novel and improved fiber packaging structures developed by the inventor are disclosed in the inventor's co-pending U.S. patent application Ser. No. 07/927,061 filed Aug. 6, 1992, and entitled "Molded Pulp Fiber Interior Package Cushioning Structures." The novel and improved packaging structures disclosed may be formed in complex shapes, including ribs, anti-hinge ribs, pods (singular or in rows), podded ribs, fillets, posts, shelves, scalloped or reinforced edges, stacking ribs and pods, crush ribs, suspension pockets, rib cages, and other complex structures.
Machines designed to form conventional paper fiber packaging structures, such as the fruit and egg cartons found in supermarkets, have been available for many years. One such machine available at a reasonable cost is a vertical motion-type low-volume vacuum molding machine made by Tomlinson's Ltd. of Rochdale, England. This machine is designed to continuously produce a desired molded fiber product.
U.S. Pat. No. 3,850,793 to Hornbostel et al. shows a molding machine for producing pulp products with a vacuum plenum divided into two chambers by a partition, with one mold mounted in each chamber. However, this machine is designed to produce a dashboard and is not adapted to form a variety of paper fiber packaging structures in the manner of the present invention.
U.S. Pat. No. 3,005,491 to Wells shows a high speed rotary type vacuum molding machine including an adapter plate secured to the periphery of a molding wheel which assists in vacuum distribution However, the Wells design is intended only to secure a single mold.
U.S. Pat. No. 3,046,187 to Leitzel discloses a fruit tray molding machine which provides additional pressure ports and conduits to form aeration holes in the molded products.
U.S. Pat. No. 3,306,815 to Mayne describes a vertical action molding apparatus with a mold assemble suspended by a "flange connection" from a telescoping vacuum delivery pipe. U.S. Pat. No. 773,671 to Palmer shows a vertical motion molding device for pressure molding embossed panels from a pulp slurry. Final compression action of the molding frame is provided manually by a catch lever with a cam face engaging the mold bed. U.S. Pat. No. 1,409,591 to Schavoir shows the use of cam faced arms to lock together two mold sections of a press mold. U.S. Pat. No. 4,306,851 to Thune describes an injection molding apparatus for automotive-type batteries with a cam acting mechanism to lock internal molding cores into desired alignment with external mold cavities before injection. U.S. Pat. No. 4,883,415 to Salvadori discloses a tire molding machine with a rapid coupling and releasing bayonet mechanism for securing parts of the tire mold. U.S. Pat. No. 3,306,813 to Reifers shows a peripheral ring bolted to a mold to form a smooth peripheral edge surface on a molded article. None of these references appears to disclose securing a mold to a platen using a camming arrangement, or the provision of quick release mechanisms to provide rapid interchangeability of different molds on a platen.
Since the novel and improved packaging structures discussed above with reference to the inventor's co-pending application are more complex than common supermarket cartons, the complexity of the manufacturing process tends to be increased. Further, the natural uniformity of eggs, for example, makes it possible to standardize their cartons, so that a machine may be dedicated to manufacturing the cartons and operated more or less continuously. However, according to the present invention, a variety of more complex packaging structures, as taught in the inventor's co-pending application, are provided for different products. The volume requirements for a given packaging structure may not justify the cost of a dedicated machine. Further, even if the machinery investment can be justified, there are substantial fixed costs in time and raw materials each time such machines are started. If the machine is used only intermittently to produce a relatively low volume output, the cost per unit is multiplied. For this reason, fiber molding machines are most efficient when operated to produce a nearly continuous output. Finally, it may be desirable in many cases to provide packaging output at a rate similar to the rate of products being produced on a parallel assembly line, so that the packaging for such products is provided "just in time" for the products to be boxed and shipped. In this way, the need for a large inventory of packaging material at the shipping site can be reduced.
For all of these reasons, it may not be desirable to dedicate a unique machine to each type of molded fiber product. Therefore, there is a need for a machine capable of manufacturing a variety of packaging shapes, which permits ready changeover of production to a new type of packaging shape without clearing and restarting the machine.